Tuesday, April 27, 2010

"A rocket carrying the Ikaros -- an acronym for Interplanetary Kite-craft Accelerated by Radiation of the Sun -- will blast off from the Tanegashima space centre in southern Japan on May 18. "Ikaros is a 'space yacht' that gets propulsion from the pressure of sunlight particles bouncing off its sail," Yuichi Tsuda, space systems expert at the Japan Aerospace Exploration Agency (JAXA), told journalists. The flexible sails, which are thinner than a human hair, are also equipped with thin-film solar cells to generate electricity to create "a hybrid technology of electricity and pressure", Tsuda said. "Solar sails are the technology that realises space travel without fuel as long as we have sunlight. The availability of electricity would enable us to navigate farther and more effectively in the solar system." Ikaros, which has cost 1.5 billion yen (16 million dollars) to develop, will be the first use of the technology in deep space, as past experiments have been limited to unfolding its sails in orbits around the Earth, said Tsuda. JAXA plans to control the path of Ikaros by changing the angle at which sunlight particles bounce off the silver-coloured sail. Ikaros will be a short cylindrical shape when it is released into space and will then extend its 14-metre (46 foot) sail, JAXA said."

This is a great step forward. On this scale, light sails offer little in the way of competition with chemical rockets. However, there is no way to eventually use the very real potential found in more advanced light sail spacecraft, unless people start building them and experimenting with designs. The theory is already mature (it has been since the mid 1980s, when much work was done to consider a Comet Halley rendezvous mission), and now it needs to be put into practice.

It would be nice to practice beaming energy to spacecraft as well. RTGs are great, but offer pretty low energy densities. The raw material, plutonium dioxide for example, is also in rather short supply right now. Nuclear fission is one possible answer for deep space, and solar panels will continue to work for space inside of the asteriod belt, but microwave beaming of energy may prove important in deep space. JIMO, a spacecraft that was planned to carry a nuclear reactor to produce the huge wattage needed to power radar (which would in turn scan the moons of Jupiter for underground water), could potentially use a large but gossamer microwave antenna that would accept energy beamed from near the Earth.